The present invention relates to a pinion stopper of an engine starter and, particularly, to such a stopper of an engine starter of an overhang type in which a pinion is arranged outwardly of a bearing for supporting the pinion.
FIG. 3 shows, in cross-section, a pinion stopper of a conventional engine starter. In FIG. 3, a rotational force of an armature shaft 2 is transmitted through a planet reduction gear mechanism (not shown) to an output shaft 1. A pinion drive shaft 3 is arranged coaxially of the output shaft 1 and is adapted to be driven by the output shaft 1, through an over-running clutch 4. The pinion drive shaft 3 has an end on which a pinion 5 is formed integrally. The pinion drive shaft 3 has an axial through hole including a large diameter portion 9 extending from the end thereof to a predetermined depth which is connected by a step portion 10 and a small diameter portion to a space large enough to receive a spline of the output shaft 1. The pinion drive shaft 3 is supported slidably axially of the output shaft 1 by a bearing 7 mounted on a front bracket 6. Sleeve metals 8 are disposed between the output shaft 1 and the small diameter portion of the pinion drive shaft 3. It should be noted that the pinion drive shaft 3 is shown in FIG. 3 in a retracted state and a protruded state. That is, a portion of the pinion drive shaft 3 shown above the output shaft 1 shows the retracted state, and that portion below the output shaft 1 shows the protruded state, although the pinion drive shaft 3 is a single solid component.
As is shown, the pinion drive shaft 3 can be moved axially within a space 11 defined by the step portion 10 and a stopper 12 mounted on the end portion of the output shaft 1. The stopper 12 is in the form of ring, and whose axial position on the output shaft is defined by a stop ring 14 fitted in a ring groove 13 formed on the end portion of the output shaft 1. In FIG. 3, a lever 15 has one end connected to a plunger 16a of an electromagnetic switch 16 and the other end connected to a rear portion of the over-running clutch 4.
In operation, when an electric motor is supplied with a current from a starter switch (not shown) through the electromagnetic switch 16, the armature shaft 2 is rotated so that the output shaft 1 is driven. At the same time, the plunger 16a of the electromagnetic switch 16 is attracted to rotate the lever 15 so that the over-running clutch 4 and the pinion drive shaft 3 are moved forward until the step portion 10 of the drive shaft 3 contacts the stopper 12 where the pinion 5 on the pinion drive shaft 3 meshes with a ring gear of an engine to start the latter.
As mentioned, the stopper 12 and the associated stop ring 14 are disposed radially inward of an end portion of the pinion gear 5. In disassembling the starter for maintenance or repair of parts, the stopper 12 can be separated easily from the stop ring 14 and moved axially rearward of the output shaft 1 into the space 11 by using a suitable jig, and pushing it in a direction shown by an arrow A. However, since the stop ring 14 itself is fitted firmly in the ring groove 13 formed on the output shaft 1 and has to be pulled out from the narrow space 11 axially, a removal operation for the stop ring 14 is usually very difficult. That is, in a conventional engine starter, the module of the pinion gear 5 is 2.11 to 2.54 which means that a diameter of the dedendum of the pinion 5 is small, and the diameter of the output shaft 1 is 9 to 13 mm. Therefore, in order to give enough mechanical strength to the pinion gear 5, a distance between the output shaft 1 and an inner surface of the large diameter portion 9 of the pinion drive shaft 3 has to become very small. Consequently, the removal operation of the stop ring 14 becomes very difficult even when a specially designed plier is used.